but the same natural forces that sustain the economy are also a source of danger. hoping to avoid a agedy, geographer patty mothes maps and monitors several volcanoes for ecuador's geophysica institute,nclu tunguhua. she is looking for any changes that might signal an eruption. moes and onofhese ways thate hat is to put a prism that's highly reflective, or a number of prisms up on the flanks of the volcano, and then, shooting with this very high-powered laser beam... narrator: the beams reflect off the prisms and back to patty's measuring device. it canetsubthanges in t shapef the mountain, changes that may forecast an eruption and save lives. their concern is based on history. inside a church, a mural recalls a deadly eruption in 1773. it happened again in 1886 and 1918. so why do people live in such a dangerous place? some people simply cannot afford to move, due to limited economic means. re, elshere,sinesses decisions to le near dangerils on attachnte balanced agast the eived risks. but perceptions often tinged . no es peligroso, no... translator: , it'sot goin